July 16, 1987, began with a light breeze, a cloudless sky, and a spirit of celebration. On that day, two hundred members of Congress boarded a special train for a journey to Philadelphia to celebrate a singular congressional anniversary.

Exactly two hundred years earlier, the framers of the U.S. Constitution, meeting at Independence Hall, had reached a supremely important agreement. Their so-called Great Compromise (or Connecticut Compromise in honor of its architects, Connecticut delegates Roger Sherman and Oliver Ellsworth) provided a dual system of congressional representation. In the House of Representatives each state would be assigned a number of seats in proportion to its population. In the Senate, all states would have the same number of seats. Today, we take this arrangement for granted; in the wilting-hot summer of 1787, it was a new idea.

In the weeks before July 16, 1787, the framers had made several important decisions about the Senate's structure. They turned aside a proposal to have the House of Representatives elect senators from lists submitted by the individual state legislatures and agreed that those legislatures should elect their own senators.

By July 16, the convention had already set the minimum age for senators at thirty and the term length at six years, as opposed to twenty-five for House members, with two-year terms. James Madison explained that these distinctions, based on "the nature of the senatorial trust, which requires greater extent of information and stability of character," would allow the Senate "to proceed with more coolness, with more system, and with more wisdom than the popular[ly elected] branch."

The issue of representation, however, threatened to destroy the seven-week-old convention. Delegates from the large states believed that because their states contributed proportionally more to the nation's financial and defensive resources, they should enjoy proportionally greater representation in the Senate as well as in the House. Small-state delegates demanded, with comparable intensity, that all states be equally represented in both houses. When Sherman proposed the compromise, Benjamin Franklin agreed that each state should have an equal vote in the Senate in all matters -- except those involving money.

Over the Fourth of July holiday, delegates worked out a compromise plan that sidetracked Franklin's proposal. On July 16, the convention adopted the Great Compromise by a heart-stopping margin of one vote. As the 1987 celebrants duly noted, without that vote, there would likely have been no Constitution.